Pecos Street Grade Separation Reline

Westminster, Colorado
Reline / Rehabilitation
Owner:
Engineer:
Contractor:
Technical Description:
  • Product: DuroMaxx® SRPE Liner Pipe
  • Diameter: 54-in.
  • Length: 168 LF
Installation:
August 2016

A 60-inch diameter reinforced concrete pipe (RCP) that separated Pecos Street from an overflow pond adjacent to Karen’s Pond was reported to be in distress. The Class V RCP had been installed in 2011 under a 30' tall MSE wall and was found to have cracks along the invert and the crown at several intervals and deformation of what should have been a round pipe was evident. There was also some worrisome longitudinal cracking that corresponded with the load bearing grade separation walls above. All of this had the Adams County Public Works Department on alert.

As these conditions continued to worsen, it was determined that a repair or replacement would soon be necessary. The County evaluated options that might be available to correct the situation through a structural repair rather than an extremely costly open cut replacement. Ultimately, they hired SEMA Construction, Inc. who worked with Contech Engineered Solutions to propose a slipline of the existing 60-inch RCP utilizing DuroMaxx® steel reinforced polyethylene (SRPE) liner pipe manufactured and supplied by Contech.

The proposed solution was reviewed and accepted by the consulting engineer, RockSol, who determined it was the best option for relining the 60-inch RCP. The structural calculations confirmed the DuroMaxx could support the dead and live loads, even without any contribution from the failing RCP. Previous discussions of potential repairs had involved developing a composite structure that would include the remaining resistance of the 60” RCP plus the inserted pipe as the structural solution. With the accelerated deterioration of the RCP, there was concern with this approach, and both the county and the engineers were excited to discover that the DuroMaxx liner pipe was a fully capable structural solution. The 80 ksi steel reinforced ribs provided the strength while the pressure rated polyethylene (PE) resin would provide the necessary durability. The use of DuroMaxx would provide a permanent structure solution.

The engineer elected to use 54-inch diameter DuroMaxx to slipline the existing 60-inch RCP. With an outer diameter (OD) of 55.5-inch and hydraulically smoother interior (Manning's "n" of 0.011 - 0.013), the efficient pipe was easily slid into place on skids by SEMA. Once installed, the liner pipe included welded coupler joints for a watertight solution which was then grouted in multiple stages with a lightweight cellular grout. Adams County was extremely pleased with the end result which provided a completely structural solution which would still attain the necessary hydraulics anticipated.

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